title: Optogenetic dissection reveals multiple rhythmogenic modules underlying locomotion.
abstract: Neural networks in the spinal cord known as central pattern generators produce the sequential activation of muscles needed for locomotion. The overall locomotor network architectures in limbed vertebrates have been much debated, and no consensus exists as to how they are structured. Here, we use optogenetics to dissect the excitatory and inhibitory neuronal populations and probe the organization of the mammalian central pattern generator. We find that locomotor-like rhythmic bursting can be induced unilaterally or independently in flexor or extensor networks. Furthermore, we show that individual flexor motor neuron pools can be recruited into bursting without any activity in other nearby flexor motor neuron pools. Our experiments differentiate among several proposed models for rhythm generation in the vertebrates and show that the basic structure underlying the locomotor network has a distributed organization with many intrinsically rhythmogenic modules.
authors.affiliation: Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, S-17177 Stockholm, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Hägglund
authors.forename: Kimberly J
authors.initials: KJ
authors.lastname: Dougherty
authors.forename: Lotta
authors.initials: L
authors.lastname: Borgius
authors.forename: Shigeyoshi
authors.initials: S
authors.lastname: Itohara
authors.forename: Takuji
authors.initials: T
authors.lastname: Iwasato
authors.forename: Ole
authors.initials: O
authors.lastname: Kiehn
mesh_terms: D000818:Animals; D008027:Light; D008124:Locomotion; D051379:Mice; D008822:Mice, Transgenic; D009415:Nerve Net; D013116:Spinal Cord / Q000502:physiology
keywords: channelrhodopsin-2; halorhodopsin; interneurons; motor neurons